Surface pH Effects on Catalytic Behavior of Pyridinic Nitrogen on Nitrogen-doped Carbon Nanotube in CO<sub>2</sub> Electrochemical Reduction

Nitrogen-doped carbon nanotubes (NCNTs) have been considered a promising catalyst for the electrochemical reduction of CO2 (CO2ER) to generate CO. Although pyridinic N sites suggested be active center NCNTs, their behavior in reaction remains unclear because lack experimental evidence. Herein we focused on pH dependence CO2ER activity NCNT and investigated effects local at electrode surface estimate catalytic role N. The results situ measurements using surface-enhanced Raman spectroscopy (SERS) revealed that disappears an acidic environment below 4. SERS detected no CO species during electrolyte, ex X-ray photoelectron indicated protonation These suggest N, site NCNT, inhibits adsorption following define activity.